[Python] Fix bug where WorkerHandlerManager.close_all re-initialized state with incorrect dict type

sdks/python/apache_beam/runners/portability/fn_api_runner/worker_handlers.py

@@ -939,7 +939,7 @@ def close_all(self):
         except Exception:
           _LOGGER.error(
               "Error closing worker_handler %s" % worker_handler, exc_info=True)
-    self._cached_handlers = {}  # type: ignore[assignment]
+    self._cached_handlers = collections.defaultdict(list)
     self._workers_by_id = {}
     if self._grpc_server is not None:
       self._grpc_server.close()

sdks/python/apache_beam/runners/portability/fn_api_runner/worker_handlers_test.py

@@ -0,0 +1,52 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# pytype: skip-file
+import logging
+import unittest
+
+from apache_beam.portability.api import beam_provision_api_pb2
+from apache_beam.runners.portability.fn_api_runner.fn_runner import ExtendedProvisionInfo
+from apache_beam.runners.portability.fn_api_runner.worker_handlers import WorkerHandlerManager
+from apache_beam.transforms import environments
+
+_LOGGER = logging.getLogger(__name__)
+
+
+class WorkerHandlerManagerTest(unittest.TestCase):
+  def test_close_all(self):
+    inprocess_env = environments.EmbeddedPythonEnvironment(
+        capabilities=environments.python_sdk_capabilities(),
+        artifacts=(),
+        resource_hints={}).to_runner_api(None)
+    envs = {
+        'inprocess': inprocess_env,
+    }
+    prov_info = ExtendedProvisionInfo(
+        beam_provision_api_pb2.ProvisionInfo(
+            retrieval_token='unused-retrieval-token'))
+
+    manager = WorkerHandlerManager(envs, job_provision_info=prov_info)
+    first_workers = manager.get_worker_handlers('inprocess', 1)
+    manager.close_all()
+    second_workers = manager.get_worker_handlers('inprocess', 1)
+    assert len(first_workers) == len(second_workers) == 1
+    assert first_workers != second_workers
+
+
+if __name__ == '__main__':
+  logging.getLogger().setLevel(logging.INFO)
+  unittest.main()